This invention relates to isolating overhead power lines.
The most common way to effect such isolation is to use an assembly which includes two full tension clamps (dead ends) and an insulator in between them. The first full tension clamp is fixed to an overhead line allowing the rest of the assembly to hang freely from the power line. In some cases hooks can support the assembly closer to the power line as to keep the assembly from hanging down and possibly making contact with live lines. A mechanical hoist is then attached to the power line away from the assembly. The other end of the hoist is then attached to the full tension clamp at the free end of the assembly. The hoist is then operated in such a fashion as to take up the assembly parallel to the power line and introduce some slack line in between the clamps at each end of the isolator assembly. The second full tension clamp is now fastened to the power line. The hoist can now be removed. The power line tension is now transferred through the isolator assembly and the short portion of line in between the two clamps bulges due to the lack of tension on that portion. This line portion can now be cut and separated to isolate the line.
The assembly is now mechanically connected between cut ends of rite line. Often the assembly also includes a switch connected in parallel across the insulator and both ends of the switch now have to be connected electrically to respective portions of the cut line. This may be done using C-shaped members and wedges.
This technique is time consuming and difficult for one man to carry out particularly because of the need for a hoist.
Another technique has been proposed in U.S. Pat. No. 4,814,530. This technique involves an isolating apparatus having clamps pivotally mounted at opposite ends of a insulator. The clamps can be secured to the power line such that the insulator lies below and parallel to the line, and thereafter the power line can be severed between the clamps. One reason that this apparatus has not found acceptance in practice is that, after the line is cut, there is an immediate and sudden straightening of the apparatus caused by the tension in the line and gives rise to severe forces in the line and particularly at the clamps.
It is an object of the invention to provide an improved isolating apparatus and method.